The thermoplastic elastomers (hereinafter abbreviated as TPE) which are industrially used at present can be roughly divided into two types: TPE comprising a block copolymer composed of soft segments and hard segments and TPE, called elastomer alloy, comprising a partially crosslinked rubber and a plastic phase-separated therefrom. As the former type, there are known, for instance, the block copolymers called polyester elastomers consisting of an aliphatic polyether portion such as polytetramethylene glycol and a polyester portion such as polyethylene terephthalate and polybutylene terephthalate, and the block copolymers called polyamide elastomers consisting of an aliphatic polyether portion and a polyamide portion such as polydodecanolactum. As the latter type, there are known, for example, the elastomer alloys comprising a dynamically vulcanized alloy of polypropylene and an ethylenepropylene-diene terpolymer.
Also, European Patent Laid-Open No. 0287233 discloses a polymer solution for coating using a copolymer having an aromatic polyester as branch polymer, namely a copolymer having an aromatic polymer covalently bonded to an acrylic resin or polyester resin, said polymer solution being characterized by being capable of forming a coat with high hardness. However, this European patent is silent on thermoplastic resins and TPE.
It is to be noted that with TPE's comprising a block copolymer composed of soft and hard segments, it is merely possible to obtain relatively hard elastomer having a Shore hardness (D scale) of about 40 or greater. Also, these TPE's take a large compression set and are not so high in thermal resistance.
On the other hand, the elastomer alloys, although capable of forming the soft elastomers having a Shore Scale A hardness of about 30, are rather poor in thermal resistance.
The object of the present invention is to provide a resin composition useful as a thermoplastic elastomer with excellent thermal resistance.